Seal plugs are sometimes required, for example, in electrical conduits provided with a connector constituted by a conduit nipple portion threaded into a conduit union part. Seal plugs may also be required for example in applications wherein cables or wires are passed through a wall of an engine bearing housing and wherein a pressure differential may exist between the sides of the wall. Such a plug may also be employed where electric cables are passed from one side of a housing to the other side of the housing. Depending on the particular application, it may be necessary to close or seal off the conduit interior in order to prevent leakage of fluid, such as gas or oil. On the other hand, or in addition, it may be necessary that cables threaded through the conduit are passed through the plug without causing abrasion and the like damage to the cable, while maintaining the sealing function of the plug.